Thursday, July 26, 2007

Ozone back in the equation?

I understood that the ozone layer being destroyed by CFCs problem had been sorted out, and that the holes were now contracting. But it now seems that ozone has yet another trick up its sleeve, this time to do with accelerating global temperatures. Full article is on the RSC - Chemistry World.

"Ozone was already known to have a significant direct greenhouse gas (GHG) action. But the new effect is an indirect one, resulting from the toxic effect of high ozone levels on land plants."

Apparently, ozone in the lower atmosphere directly affects the way that plants absorb CO2, reducing the land carbon sink capability.

"Land plants absorb CO2 through pores in their leaves called stomata. When atmospheric ozone levels reach about 40ppm - already reached in many parts of the world - these stomata contract, reducing the plants' CO2 uptake. Moreover, ozone levels are expected to reach 70ppm in many parts of the world by the year 2100. This will suppress the land carbon sink, push up the equilibrium level of atmospheric CO2, and boost the greenhouse effect"

This "could boost average world temperatures by a further 0.5-1.25°C - compared with the 2-5°C that will result from a doubling of atmospheric CO2."

This appears to suggest that things could get even worse than predicted; but no doubt there will be some counter argument that suggests that this is all a load of guff too!

Is it just one more straw on the camel's back to worry about?

ADDENDUM 1 (from Junkk Male):

Real Climate: Ozone impacts on climate change
The Ecologist: Rising ozone levels could stunt plant growth


Peter said...

Well, it starts with the now well familiar 'could', so there is some hope.

It will be interesting to see how this gets picked up on elsewhere, and interpreted by those better qualified than I to comment.

Certainly worth bearing in mind. I hadn't appreciated that ozone was still being churned out in such damaging quantities industrially.

What's the betting that, if it is this significant, the next campaign we'll be subjected to is banning kebabs (bad example, as our omnivorous ways, though entirely 'natural', are probably high on both the individual and industrial levels in combination to represent a very bad enviROI. And those burners...oi!).

I can't say that, all things considered, I could pass the story on as requested under the banner at the end as 'enjoyed'.

Lawrence Clark said...

The article wasn't that clear about where ozone occurs in the atmosphere. The ozone layer, which protects us from extremes of UV, and was threatened by CFCs, is in the stratosphere.

Low level ozone, on the other hand, is produced as part of photochemical smogs, and requires sunlight, hydrocarbons (e.g. petrol) and oxides of nitrogen. Link below goes more into the science of this:

It's been known for some time (many years) that ozone at ground level is poisonous to plants, as well as to people. I see that underlying this story is a paper in Nature, where they have calculated how this poisonous effect might affect the ability of plants to take up CO2.....As ozone is also a greehhouse gas, this is a greenhouse 'double whammy'.

Technical innovations to tackle low level ozone include catalytic converters in cars (late 20th Century), electric trains (including the tube) (19th Century) and shanks pony (Neanderthal).